chore(dependencies): update Keycloak version

* update Keycloak version
* adapt code ans services conf to new keycloak version
Can't update to Keycloak 22.x as it no longer supports Java 11
fix several CVEs

Covers [RUNTIME-1742](https://bonitasoft.atlassian.net/browse/RUNTIME-1742)

Report of bonitasoft/bonita-web-sp@8018565

buildSrc/src/main/groovy/Deps.groovy

@@ -62,7 +62,7 @@ class Deps {
     public static String hamcrestVersion = "2.1"
     public static String woodstoxCoreVersion = "6.4.0"
     public static String woodstoxStax2ApiVersion = "3.1.4"
-    public static String keycloakVersion = "20.0.3"
+    public static String keycloakVersion = "21.1.2"
     public static String spnegoVersion = "1.1.1"
 
     // Test dependency versions: